1. Field of the Invention
The present invention relates to a method for producing MEMS structures, in particular using CMOS processes, and a method for combined production of a CMOS structure and a MEMS structure.
2. Description of the Related Art
At the present time, microelectromechanical (MEMS) structures are frequently produced using CMOS technology. The metal printed conductors employed in a CMOS process may be used as movable structures as well as for forming electrodes. The dielectric layers, in particular the oxide layers, situated beneath the metal printed conductors may be used as a sacrificial layer in order to partially or completely leave the metal printed conductors open. With the aid of the CMOS technology, together with the MEMS structures, standard switching elements may also be produced which take over the control and evaluation of the MEMS element within a chip.
One important aspect in the use of metal printed conductors in MEMS structures is typically their mechanical properties, such as plasticity, brittleness, flexural strength, breaking strength, and the like. Another aspect is that vertically high structures having a height of greater than 5 μm and high aspect ratios (ratio of the vertical to the lateral extension) are not producible using conventional CMOS technology.
Another approach concerns the design of metal printed conductors which remain connected to a silicon substrate via oxide layers. With the aid of etching processes, the silicon in the substrate may be appropriately structured in order to form supporting silicon webs beneath the metal printed conductors. Published German patent application document DE 10 2008 054 553 A1, for example, discloses an acceleration sensor having movable and stationary electrodes in a substrate.
Published German patent application document DE 10 2006 051 597 A1 discloses a semiconductor system having a cantilevered microstructure above a substrate.
Front- and back-side processes are frequently necessary for producing MEMS structures, in particular in the production of undercut silicon structures for cantilevered elements.